Sirloin is my favorite steak and Noah hits a home run here. If you want to do this and don't have any lemons, try substituting vinegar. I'm not kidding. I've used vinegar as the acid ingredient in my steak marinade for years and it works. No, the steak doesn't have a vinegar flavor unless you add way too much. A couple of tablespoons will do it for a 1 gallon plastic bag full of steak. I did this last week with a London Broil and had great results, too
Hint: Add a couple of tablespoons of EVOO, too.
Hub